Is it possible to access old data state in an DB2 database?
Oracle has the clause select ... as of timestamp to do it. Does DB2 have something like it?
Yes, you can select a set of rows that were / will be valid in a past / future time. This is called Time Travel in DB2, but you have to configure / create the table with the extra columns in order to activate this feature. This is new in DB2 10, but I think it is not available in all editions.
For more information, take a look at this: http://www.ibm.com/developerworks/data/library/techarticle/dm-1204db2temporaldata/
Remember, there are two concepts: business time and application time, and when using both is called bi-temporal.
Related
I am using DB2 9.7 (LUW) in a windows server, in which multiple DBs are available in a single DB instance. I just found that in one of these DBs, I am unable to add a column with DATE data type, during table creation or altering. The column been added is getting changed to timestamp instead.
Any help on this will be welcome.
Check out your Oracle Compatibility setting
Depending on that setting a date is interpreted as Timestamp(0) like in your example.
Because these settings take effect if the database has been created after setting the DB2_COMPATIBILITY_VECTOR registry variable your database can show a different behaviour.
I am new to tableau, gone through the site before having this question posted, didn't found answer matching to my question.
I have connection established successfully to Cassandra using "DataStax cassandra ODBC driver 64bit windows", evrything is fine, filled all details like "keyspace name, table name as per documentation available in Datastax site".
But when I drag the available table to canvas it's keep on loading for minutes, what the database guy has told me about the data is it's more millions of data for one day, so we have 6months data and that to data gets updated for every 10 minutes, it;s for a reputed wind energy company.
My client has given me "" CQL used for creating table:
create table abc_data_test.machine_data
(machine_id text, tag text, timestamp timestamp, value double,
PRIMARY KEY((machine_id, tag), timestamp))
WITH CLUSTERING ORDER BY(timestamp DESC)
AND compression = { 'sstable_compression' : 'LZ4Compressor' };"".
Where to keep this code?
I tried to insert in connection page it's giving a error. I am getting a new custom sql error (I placed the code in "new custom sql" ) .
The time is still running, can be seen as:
processing request: connecting to datasource, Elapsed time 87:09
The error from new custom sql is
An error occured while commuicating with the datasource. [DataStax][CassandraODBC] (10) Error while executing a query in Cassandra:33562624: line 1.11 no viable alternative at input '1' (SELECT [TOP]1...)
I'm using windows 10 64bit, DataStax odbc driver 64bit-2.4.1 version,DSE is4.8 and later .
You cannot pass DDL sql into the custom sql box. If the Cassandra connection supports the Initial SQL option, you could pass it there. Then your custom sql would be some sort of select statement. Otherwise, create the table in Cassandra then connect to that table from Tableau.
i have a DB2 data source and an Oracle 12c target.
The Oracle has a DB link to the DB2 defined which is working in general.
Now i have a huge table in the DB2 which has a timestamp column (lets call it ROW_CHANGED) for row changes. I want to retrieve rows which have changed after a particular time.
Running
SELECT * FROM lib.tbl WHERE ROW_CHANGED >'2016-08-01 10:00:00'
on the DB2 returns exactly 1 row after ca. 90 secs which is fine.
Now i try the same query from the Oracle via the db link:
SELECT * FROM lib.tbl#dblink_name WHERE ROW_CHANGED >TO_TIMESTAMP('2016-08-01 10:00:00')
This runs for hours and ends up in a timeout.
I read some Oracle docs and found distributed query optimization tips but most of them refer to joining a local to a remote table which is not my case.
In my desperation, i have tried the DRIVING_SITE hint, without effect.
Now i wonder when the WHERE part of the query will be evaluated. Since i have to use Oracle syntax and not DB2 syntax for the query, is it possible the Oracle will try to first copy the full table and apply the where clause afterwards? I did some research but did not find anything which would help me in this direction.
The ROW_CHANGED is a hidden column in the DB2, if that matters.
Thx for any hint in advance.
Update
Thanks#all for help. I'll share what did the trick for me.
First of all i have used TO_TIMESTAMP since the DB2 column is also Timestamp (not date) and i had expected to circumvent implicit conversions by this.
Without the explicit conversion i ran into ORA-28534: Heterogeneous Services preprocessing error and i have no hope of touching the DB config within reasonable time.
The explain plan btw did not bring much. It showed a FULL hint and no conversion on the predicates. Indeed it showed the ROW_CHANGED column as Date, i wonder why.
I have tried Justins suggestion to use a bind variable, however i got ORA-28534 again. Next thing i did was to wrap it into a pl/sql block (will run in a SP anyway later).
declare
v_tmstmp TIMESTAMP := 01.08.16 10:00:00;
begin
INSERT INTO ORAUSER.TMP_TBL (SRC_PK,ROW_CHANGED)
SELECT SRC_PK,ROW_CHANGED
FROM lib.tbl#dblink_name
WHERE ROW_CHANGED > v_tmstmp;
end;
This was executing in the same time as in DB2 itself. The date format is DD.MM.YY here since it is the default unfortunately.
When changing the variable assignment to
v_tmstmp TIMESTAMP := TO_TIMESTAMP('01.08.16 10:00:00','DD.MM.YY HH24:MI:SS');
I got the same problem as before.
Meanwhile the DB2 operators have created an index in the ROW_CHANGED column which i requested earlier that day. This has solved the problem in general it seems. Even my original query finishes in no time now.
If you are actually using an Oracle-specific conversion function like to_timestamp, that forces the predicate to be evaluated on the Oracle side. Oracle isn't going to know how to convert a built-in function like to_timestamp into an exactly equivalent function call in DB2.
If you used a bind variable, that would be more likely to get evaluated on the DB2 side. But that may be complicated by the data type mapping between different databases-- there may not be a perfect mapping between one engine's date and another engine's timestamp data type. If this was a numeric column, a bind variable would be almost certain to get pushed. In this case, it probably involves playing around a bit to figure out exactly what data type to use for your variable that works for your framework, Oracle, and DB2.
If using a bind variable doesn't work, you can force the predicate to be evaluated on the remote server using the dbms_hs_passthrough package. That lets you send a query verbatim to the remote server which allows you to do things like use functions defined in your DB2 database. That's a bit of overkill in this situation, hopefully, but it's nice to have the hammer as your backup if the simpler solution doesn't work quickly enough.
I am currently experimenting with Tableau Extract API to generate some TDE from the tables I have in a PostgreSQL database. I was able to write a code to generate the TDE from single table, but I would like to do this for multiple joined tables. To be more specific, if I have two tables that are inner joined by some field, how would I generate the TDE for this?
I can see that if I am working with small number of tables, I could use a SQL query with JOIN clauses to create a one gigantic table, and generate the TDE from that table.
>> SELECT * FROM table_1 INNER JOIN table_2
INTO new_table_1
ON table_1.id_1 = table_2.id_2;
>> SELECT * FROM new_table_1 INNER JOIN TABLE_3
INTO new_table_2
ON new_table_1.id_1 = table_3.id_3
and then generate the TDE from new_table_2.
However, I have some tables that have over 40 different fields, so this could get messy.
Is this even a possibility with current version of the API?
You can read from as many tables or other sources as you want. Or use complex query with lots of joins, or create a view and read from that. Usually, creating a view is helpful when you have a complex query joining many tables.
The data extract API is totally agnostic about how or where you get the data to feed it -- the whole point is to allow you to grab data from unusual sources that don't have pre-built drivers for Tableau.
Since Tableau has a Postgres driver and can read from it directly, you don't need to write a program with the data extract API at all. You can define your extract with Tableau Desktop. If you need to schedule automated refreshes of the extract, you can use Tableau Server or its tabcmd command.
Many thanks for your replies. I am aware that I could use Tableau Desktop to define my extract. In fact, I have done this many times before. I am just trying to create the extracts using the API, because I need to create some calculated fields, which is near impossible to create using the Tableau Desktop.
At this point, I am hesitant to use JOINs in the SQL query because the resulting table would look too complicated to comprehend (some of these tables also have same field names).
When you say that I could read from multiple tables or sources, does that mean with the Tableau Extract API? At this point, I cannot find anywhere in this API that accommodates multiple sources. For example, I know that when I use multiple tables in the Tableau Desktop, there are icons on the left hand side that tells me that the extract is composed of multiple tables. This just doesn't seem to be happening with the API, which leaves me stranded. Anyways, thank you again for your replies.
Going back to the topic, this is something that I tried few days ago on my python code
try:
tdefile= tde.Extract("extract.tde")
except:
os.remove("extract.tde")
tdefile = tde.Extract("extract.tde")
tableDef = tde.TableDefinition()
# Read each column in table and set the column data types using tableDef.addColumn
# Some code goes here...
for eachTable in tableNames:
tableAdd = tdeFile.addTable(eachTable, tableDef)
# Use SQL query to retrieve bunch_of_rows from eachTable
for some_row in bunch_of_rows:
# Read each row in table, and set the values in each column position of each row
# Some code goes here...
tableAdd.insert(some_row)
some_row.close()
tdefile.close()
When I execute this code, I get the error that eachTable has to be called "Extract".
Of course, this code has its flaws, as there is no where in this code that tells how each table are being joined.
So I am little thrown off here, because it doesn't seem like I can use multiple tables unless I use JOINs to generate one table that contains everything.
The question pretty much sums it up. I've got to replace text in a large number for store procedures. Its not so many that doing it manually is impossible, but enough that I'm asking the question. I also prefer automation as it reduces the change of user error when we make the change in production.
I can Identify them like this:
select OBJECT_DEFINITION(object_id), *
from sys.procedures
where OBJECT_DEFINITION(object_id) like '%''MyExampleLiteral''%'
order by name
Is there any way to mass update them all to change 'MyExampleLiteral' to 'MyOtherExampleLiteral'?
I'd even settle for a way to open all the stored procs. Just Finding these store procs in a larger list will take some time.
I thought about generating alter statements using the above select statements, but then I lose line breaks.
Thanks in advance,
This is a Microsoft SQL Server.
There are different tools to use depending on the database in question. For example, Microsoft SQL Server Data Tools integrates with Visual Studio, and allows you to do these types of operations fairly easily. The database is stored in your solution as scripts, which you can then search and replace any keyword you wish. I'm assuming there would be similar tools available for other platforms.
You could do this with dynamic sql. Query the system tables to get all the SPs containing your "MyExampleLiteral":
SELECT [object_id] FROM sys.objects o
WHERE type_desc = 'SQL_STORED_PROCEDURE'
AND is_ms_shipped = 0
AND OBJECT_DEFINITION(o.[object_id]) LIKE '%<search string>%'
Then, write a while loop to go through those object_ids. In the while loop, get the OBJECT_DEFINITION() into a string and replace the "MyExampleLiteral", then replace CREATE PROCEDURE with ALTER PROCEDURE and execute the string using sp_executesql.
Doing something this crazy, make sure you backup the database first.